1. Field of the Invention
The present invention is broadly concerned with an improved sow lactation diet especially designed for use with relatively high protein swine diets containing soybean and corn proteins in order to enhance pig and litter weaning weights, particularly with high producing sows. More particularly, the invention pertains to a sow lactation diet, and a corresponding method, wherein the diet containing from about 0.01-1.2% by weight synthetic valine includes from about 12-30% by weight of total protein (generally obtained from corn and soy), a total lysine content of at least about 0.75% by weight.
2. Description of the Prior Art
It is generally understood among swine nutritionists that the amino acid requirements for lactating sows can be considered as that needed for maintenance on the one hand and milk production on the other. This is the approach taken by the Agricultural Research Council in "The Nutrient Requirements of Pigs" (1981). Since the amino acid maintenance requirements of swine are relatively small and constant, larger quantities of amino acid are needed during lactation to support milk production, as compared with maintenance.
The valine content of sow's milk is low as compared with lysine (normally about 63% of the lysine content). Based upon this information, the ARC in 1981 estimated that the valine requirement during lactation is 70% of the lysine requirement. This in turn indicates that valine is not an important or primary limiting amino acid in sow lactation diets. Rather, using the ARC recommendations, the order of importance for amino acids in a corn-soybean meal diet would be lysine, threonine, isoleucine, methionine, tryptophan and valine, respectively. Accordingly, valine is not presently being added to sow lactation diets, because of the feeling that adequate valine is provided as a naturally occurring amino acid in normal swine diet ingredients.
Rousselow and Spear in "Valine Requirement of the Lactating Sow", Journal of Animal Science, Vol. 50, No. 3, p. 472-478 (1980) describe an experiment wherein a low protein test diet (about 11.49% by weight protein derived primarily from corn) was supplemented with various levels of valine in an attempt to determine optimum valine levels. Their findings suggest a preferred valine level for lactating sow diets between 0.53% and 0.68%. However, these workers did not employ a typical swine diet including soybean protein, and the sows were nursing an average of only 7.5 pigs. Moreover, genetic improvements in modern-day swine herds render this data obsolete.